Resurecting this to say it's still in 31.12.
I have an epic entry hall, with 2 z-levels of fortification looking out in a hallway to eventually be covered with ballistias.
There is a problem with archery though... You see, my Marksdwarf doesn't shoot.
The Ammunition assignment is just fine. He shoots if sent out into the entry hall, but not if he is assigned to the balcony walkways, regardless of the Z level.
I think I know the problem though. Unless he is standing EXACTLY next to a fortification, he cannot engage the enemy. This is normally not an issue with squads of 10 marksdwarves. SOMEONE will be standing next to the fortification and get the squad to react. However, if you have a single individual or only a few, the spacing of random positioning will have them standing up to several steps away from the fortification. They do not rush to the fortification to protect against others being shot either. As such, unless your marksdwarf is standing immediately next to the fortification, there is no interaction between him and the enemy unless there is pathing to them to engage the fighting.
So if you want your dwarves to shoot, you need to ensure that they stand exactly by the fortification you want them to shoot out of. If they don't, they won't even engage the enemy. It has proven true in every test I have tried.
Edit: More testing shows that once the dwarf has considered himself in combat with them, he will pursue them along complex fortification routes and fire normally, even if they run away and return.
What I mean by this is I had a marksdwarf stationed in my upper pilboxes next to a fortification. He caught sight of them and "engaged" them with a single arrow, and then they were out of range of the pillbox. He then went through my winding path down to the upper balcony and engaged them from the upper balcony gallery. They ran off and regrouped, then returned and he engaged them right away. It's only the initial engagement that is having difficulty.